[Leetcode] [Javascript]4sum

4Sum 

Given an array S of n integers, is there elements a, b, C, and D in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target.

Note:

• Elements in a quadruplet (a,b,c,D) must is in non-descending order. (ie, a ≤ b ≤ c ≤ d)
• The solution set must not contain duplicate quadruplets.

https://leetcode.com/problems/4sum/

I see tags have hashtable, think of the triple cycle is not used, there is no use of this solution.

First 22 merge, and then use the double pointer to find the result.

Although the AC, but wrote a lot of good sad, but also not fast, below the average level, this is not the same as agreed (╯‵-′) ╯︵┻━┻, it must be used in the wrong posture.

1 /**2 * @param {number[]} nums3 * @param {number} target4 * @return {number[][]}5  */6 varFoursum =function(nums, target) {7Nums =nums.sort (sorting);8     varresult = [];9     varCountappear = {}; Twosummap = {}, Twosumarr = [];Ten     varIsfound =NewSet (); One     varI, J, Twosum; A      for(i = 0; i < nums.length; i++){ -         if(!Countappear[nums[i]]) { -Countappear[nums[i]] = 1; the}Else{ -countappear[nums[i]]++; -         } -          for(j = i + 1; j < Nums.length; J + +){ +Twosum = Nums[i] +Nums[j]; -             if(!Twosummap[twosum]) { + Twosumarr.push (twosum); ATwosummap[twosum] =[{small:nums[i], large:nums[j]}]; at}Else if(!Arrcontains (Twosummap[twosum], nums[i], nums[j])) { - Twosummap[twosum].push ({small:nums[i], large:nums[j]}); -             } -         } -     } -Twosumarr =twosumarr.sort (sorting); in      -     varNumA, NumB, SUM4, TMP, join; to      for(i = 0, j = twosumarr.length-1; I <=J;) { +NumA = Twosummap[twosumarr[i]], NumB =Twosummap[twosumarr[j]]; -SUM4 = Twosumarr[i] +Twosumarr[j]; the         if(Sum4 = = =target) { * addcandidate (NumA, NumB, result); $         }Panax Notoginseng         if(Sum4 <target) { -i++; the}Else{ +j--; A         } the     } +     returnresult; -      $     functionVerifyresult (arr) { $         varPrevious =NULL, Count = 0; -          for(vari = 0; i < arr.length; i++){ -             if(Arr[i]!==Previous) { thePrevious =Arr[i]; -Count = 1;Wuyi}Else{ thecount++; -                 if(Count >Countappear[previous]) { Wu                     return false; -                 } About             } $         } -         return true; -     } -     functionaddcandidate (NumA, NumB, result) { A         varI, J; +          for(i = 0; i < numa.length; i++){ the              for(j = 0; J < Numb.length; J + +){ -TMP =[Numa[i].small, Numa[i].large, Numb[j].small, Numb[j].large]; $TMP =tmp.sort (sorting); the                 if(Verifyresult (tmp)) { theJoin = Tmp.join (' # '); the                     if(!Isfound.has (join)) { the Isfound.add (join); - Result.push (TMP); in                     } the                 }             the             } About         } the     } the     functionarrcontains (arr, small, Large) { the          for(vari = 0; i < arr.length; i++){ +             if(Arr[i].small = = = Small && Arr[i].large = = =Large) { -                 return true; the             }Bayi         } the         return false; the     } -     functionsorting (A, b) { -         if(A >b) { the             return1; the}Else if(A <b) { the             return-1; the}Else{ -             return0; the         } the     } the};

[Leetcode] [Javascript]4sum